Paper layers laminated by polyethylene layer

ABSTRACT

A LAMINATED TISSUE AND POLYALKYLENE PAPER PRODUCT AND A METHOD OF MAKING IT. THE LAMINATE SHEET MATERIAL COMPRISES TWO SHEETS OF TISSUE PAPER BONDED TOGETHER BY AN INTERMEDIATE, CONTINUOUS POLYALKYLENE LAYER WHICH IS SUBSTANTIALLY COMPLETELY IMPREGNATED SUBSTANTIALLY EQUALLY INTO THE ADJACENT TISSUE SURFACES WITHOUT PENETRATING THROUGH TO THE EXTERIOR SURFACES OF THE LAMINATE. TWO OPPOSED WEBS OF TISSUE PAPER AND A SUBSTANTIALLY CONTINUOUS CURTAIN OF MOLTEN POLYALKYLENE ARE FED INTO THE NIP OF A PAIR OF COACTING PRESSURE ROLLERS. THE RATE OF MOLTEN POLYALKYLENE FLOW IS REGULATED IN THE RANGE OF FROM ABOUT 20% TO ABOUT 30% OF THE TOTAL WEIGHT OF THE LAMINATE, AND THE PRESSURE OF THE ROLLERS AGAINST THE WEBS PASSING THEREBETWEEN IS REGULATED TO FEED SAID WEBS THROUGH THE NIP WITHOUT SLIPPAGE RELATIVE THERETO AND TO FORCE SAID WEBS INTO SUBSTANTIAL CONTIGUITY, WITH THE POLYALKYLENE SUBSTANTIALLY COMPLETELY IMPREGNATED INTO BUT NOT COMPLETELY THROUGH SAID WEB.

w. H. STEPP 3,684,643

PAPER LAYERS LAMINATED BY POLYETHYLENE LAYER Aug. 15, 1972 Filed Nov. 17, 1969 INVENTOR.

h/'A/OAEZZ. 194 $7672 AT'fOPA/E YE United States Patent Ofifice 3,684,643 Patented Aug. 15, 1972 3,684,643 PAPER LAYERS LAMINATED BY POLYETHYLEN E LAYER Wendell H. Stepp, Dotlran, Ala., assignor to Akwell Industries Incorporated, Dothan, Ala. Filed Nov. 17, 1969, Ser. No. 877,084 Int. Cl. B32b 3/26, 27/10 US. Cl. 161-160 5 Claims ABSTRACT OF THE DISCLOSURE A laminated tissue and polyalkylene paper product and a method of making it. The laminate sheet material comprises two sheets of tissue paper bonded together by an intermediate, continuous polyalkylene layer which is substantially completely impregnated substantially equally into the adjacent tissue surfaces without penetrating through to the exterior surfaces of the laminate.

Two opposed webs of tissue paper and a substantially continuous curtain of molten polyalkylene are fed into the nip of a pair of coacting pressure rollers. The rate of molten polyalkylene flow is regulated in the range of from about 20% to about 30% of the total weight of the laminate, and the pressure of the rollers against the Webs passing therebetween is regulated to feed said webs through the nip without slippage relative thereto and to force said webs into substantial contiguity, with the polyalkylene substantially completely impregnated into but not completely through said webs.

BACKGROUND OF THE INVENTION This invention relates, as indicated, to a laminated tissue and polyalkylene paper product and to a method of making it.

The use of polyalkylenes for coating paper to be used as packaging and protective wrapping materials is a well known and practiced art. In this instance, appropriate polyalkylenes include those in which the monomer unit includes from 2 to 4 carbon atoms such as polyethylene and polypropylene, copolymers of ethylene and propylene, polybutylene and polyisobutylene. For example, polyethylene has been recognized as a highly suitable material due to its physical and chemical characteristics. Polyethylene is tough, extensible, abrasion-resistant, nontoxic, chemically inert to a wide range of chemical materials, and impervious to water. In addition, it may be readily extrusion-coated onto a paper web so as to render it an exceptionally suitable material for packaging and wrapping uses.

As indicated above, polyalkylenes generally, and polyethylene in particular, are impervious to water and most liquids, causing such to flow along the coated paper surface of the packaging or wrapping material. When a sealed packaging container is used, the liquid flow along the container surface is of no consequence, as it cannot gain entrance to the interior of the sealed package. However, where it is not practical nor convenient to use a sealed container, as in the case of wrapped surgical gloves, such liquid flow along the wrapping material surface is undesirable. In this instance, liquid flow along the surface of the wrapping material would result in the fluid acquiring access to the interior of the package and the sterilized contents. This problem was formerly alleviated through the use of heavy tissue paper, which prevented liquid flow on the surface but did not prevent direct penetration by the liquid to the package interior by means of capillary action. The heavy tissue was also unsatisfactory with respect to its bulk and folding characteristics, as it tended to return to its closed wrapping configuration when the package was opened by unfolding. Thus, the heavy tissue hindered the removal of the package contents.

SUMMARY OF THE INVENTION This invention, in one of its aspects, provides a unique and novel polyalkylene and tissue paper-laminated sheet material. The laminated sheet material structure is characterized by two substantially contiguous laminae of tissue paper bonded together by a continuous and substantially completely impregnated layer of polyalkylene. The polyalkylene is substantially equally impregnated into each of the two adjacent interior tissue paper web surfaces without completely penetrating through to the exterior surfaces of the laminate sheet material. With respect to the problems indicated above, the laminate sheet material provides a unique combination of lightweight characteristics, strength, folding and unfolding properties, surface absorbency, and resistance to penetration by moisture contacting and being absorbed by the paper surface.

In particular, the laminate sheet provides a stronger and more tear-resistant wrapping material than the ordinary heavy tissue paper formerly used. In addition, the laminate sheet material has a reduced tendency to return to its folded, closed position when unfolded and opened so as to facilitate the removal of the wrapped contents. The laminate sheet material also provides a water-impervious wrapping but does not allow water flow along the surfaces, as both surfaces of the laminate are substantially free of polyalkylene and retain tissue paper absorbency characteristics. This unique combination of properties provides a highly useful packaging and wrapping material which has been found particularly valuable for wrapping surgical gloves. Although the laminate sheet material of this invention is particularly suitable for that purpose, its utility is not limited to that particular end use.

In another of its aspects, this invention provides a method for producing such a laminate sheet material using conventional web laminating apparatus. A particularly suitable apparatus includes two tissue paper web supply rolls which continuously feed two opposed webs into a nip formed by a pair of coacting pressure rollers. As the webs enter the nip, the polyalkylene is also introduced into the nip between the converging webs. It is introduced as a substantially continuous curtain of molten polyalkylene extending across the width of the webs. The weights of tissue paper and polyalkylene and the relative rates of tissue paper web feeds and pressure roller advance, as well as the nip pressure, when properly adjusted as hereinafter explained, will provide the laminate sheet structure described above.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic, elevational view of apparatus which may be used to practice this invention.

FIG. 2 is a schematic, edge view of the laminated sheet material showing intermediate, impregnated polyalkylenetissue zones and the exterior tissue paper zones free of polyalkylene.

DETAILED DESCRIPTION OF THE DRAWINGS Referring now to the drawings in greater detail, FIG. 1 shows a conventional apparatus which may be used to prepare a laminated sheet material, generally at 10. There are provided two tissue paper supply rolls 12 and 14 which are arranged so as to continuously feed two tissue paper webs 16 and 18 towards each other. The tissue paper webs travel into the nip 20 between a pair of coacting pressure rollers 22 and 24. There is also provided a substantially continuous curtain of molten polyalkylene 26 which flows into the nip with and between the two tissue paper webs.

It has been found that a particularly suitably laminate sheet material is produced when each of the tissue paper webs is from about eight pounds per ream to about 1 2 pounds per ream and the polyalkylene impregnated therein is in the amount of from about five to about nine pounds per ream of the laminated material. To this end, the curtain of molten polyalkylene is provided by an adjustable supply means 28, such supply means being known to a person skilled in the art. The supply means is ad usted so as to provide a rate of flow of molten polyalkylene 1n the range of from about 20% to about 30% of the total weight of the material moving into the nip.

The pressure and rate of advance of the coacting pressure rollers are regulated with respect to the tissue paper webs and polyalkylene passing therebetween so as to feed the webs through the nip without slippage occurring between the pressure rollers. It is also necessary to regulate the pressure and rate of advance of the coacting pressure rollers to limit the amount of penetration by the polyalkylene into the adjacent interior surfaces of the tissue paper webs in order to avoid complete impregnation of one or both of the tissue webs. When proper operating conditions are achieved, the laminated sheet material will have a configuration as illustrated in FIG. 2.

As shown in FIG. 2, the tissue paper webs are in substantial contiguity and there is no distinct layer composed substantially of polyalkylene. The line A-A in FIG. 2 approximates a hypothetical interior interface of the original tissue paper webs. The polyalkylene is substantially completely impregnated in a substantially equal amount into each of the two adjacent tissue paper Web surfaces. The layer of polyalkylene impregnated into the two tissue paper webs is designated 30. The exterior surfaces 32 and 34 of the laminated sheet material are substantially free of polyalkylene and therefore retain the liquid absorbing characteristics of tissue paper. Thus, the laminate sheet material, while essentially impervious to water and most other liquids by virtue of the continuous polyalkylene impregnated layer, retains the absorbing characteristics of tissue paper as well as attaining other advantages are previously described.

What is claimed is:

1. A laminated sheet material that is both surface absorbent and impenetrable by water or the like comprising two contiguous laminae of tissue paper bonded together by a layer of thermoplastic material such as polyethylene or the like that is completely impregnated into said laminae a substantially equal distance from the adjacent surfaces of said tissue paper without penetrating through to the opposed outer surfaces of said tissue paper providing a single central composite layer of thermoplastic material and fibers having substantial thickness relative to the total thickness of the laminate, and said thermoplastic material constituting between about 20% and 30% of the total weight, said composite layer being free of water transferring fiber flow paths therethrough so that it prevents fiow of water from one outer surface of said lamimate to the other outer surface thereof, the remainder of said laminate providing a layer adjacent to each outer surface which is substantially free of said thermoplastic material and which is water absorbent to thereby impede the flow of water or the like along the surface, said laminate providing good folding and unfolding properties for packaging, whereby mere mechanical folding provides a substantially water shielding package.

2. A laminated sheet material according to claim 1 in which each of said laminae is from eight-pound per ream to 12-pound per ream tissue paper having said thermoplastic material impregnated therein in the amount of from five to nine pounds per ream of the laminated material.

3. A laminated sheet material that is both surface absorbent and impenetrable by water or the like comprising two contiguous laminae of tissue paper bonded to gether by a layer of thermoplastic material such as polyethylene or the like that is completely impregnated into said laminae a substantially equal distance from the adjacent surfaces of said tissue paper without penetrating through to the opposed outer surfaces of said tissue paper providing a single central composite layer of thermoplastic material and fibers having a major thickness relative to the total thickness of the laminate, said composite layer being free of water transferring fiber flow paths therethrough so that it prevents flow of water from one outer surface of said laminate to the other outer surface thereof, the remainder of said laminate providing a layer adjacent to each outer surface which is substantially free of said thermoplastic material and which is water absorbent to thereby impede flow of water or the like along the surface, said laminate providing good folding and unfolding properties.

4. A laminated sheet material according to claim 3 in which each of said laminae is from eight-pound per ream to 12-po-und per ream tissue paper having said thermoplastic material impregnated therein in the amount of from five to nine pounds per ream of the laminated material.

5. A laminated material according to claim 3 in which said thermoplastic material constiutes between about 20 percent and about 30 percent by weight of the laminated material.

References Cited UNITED STATES PATENTS 3,536,563 10/1970 Brandts et a1 161-250 X FOREIGN PATENTS 790,557 7/1968 Canada 161-250 ROBERT F. BURNETT, Primary Examiner C. B. COSBY, Assistant Examiner US. Cl. X.R.

161-456, 164, 250, 400; 1l776 P, A, 143 A, 161 H; 156244, 307, 324, 334 

